Method for neurological stimulation of peripheral nerves to treat pain

ABSTRACT

According to one embodiment, a system for neurological stimulation of peripheral nerve fibers is provided. The system includes stimulation electrodes adapted to be implanted in tissue proximate a network of peripheral nerve fibers located in and innervating a painful region of a patient&#39;s body and to deliver electrical stimulation pulses to the network of peripheral nerve fibers located in and innervating the painful region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/948,134, filed Nov. 30, 2007, pending, which is a continuation ofU.S. application Ser. No. 11/066,669, filed Feb. 25, 2005, now Pat. No.7,324,852, which claims the benefit of U.S. Provisional Application No.60/547,506, filed Feb. 25, 2004, the disclosures of which areincorporated herein by reference.

TECHNICAL FIELD

This invention relates generally to therapeutic neurological stimulationand in particular to a system and method for neurological stimulation ofperipheral nerves to treat low back pain.

BACKGROUND

Neurological stimulation may be applied to specifically targeted nervetissue in the spinal cord or a particular identified peripheral nerve totreat regions of the body affected by chronic pain from a variety ofetiologies. According to one technique, a set of efficaciousneurological stimulation parameters are determined, the set ofparameters is entered into a stimulation system, and the stimulationsystem is used to electrically or chemically stimulate the specificallytargeted nerve tissue in the spinal cord or particular identifiedperipheral nerve according to the set of stimulation parameters.

For electrical stimulation, typically, an implanted pulse generatortransmits a pulse of electrical energy to an implanted electricalstimulation lead according to the set of stimulation parameters and, inresponse to the pulse, the electrodes of the implanted stimulation leaddeliver the electrical energy to the specifically targeted nerve tissuein the spinal cord or particular identified peripheral nerve. Theelectrical energy stimulates the specifically targeted nerve tissue inthe spinal cord or particular identified peripheral nerve to cause asubjective sensation of numbness or tingling in the affected region ofthe body, known as “paresthesia,” which masks or otherwise relieves painin the affected region. For example, the electrodes may be locatedexternal to the dura adjacent the specifically targeted nerve tissue inthe spinal cord that is to be stimulated. The electrodes typically mustbe precisely positioned based on the location of the specificallytargeted nerve tissue in the spinal cord or particular identifiedperipheral nerve.

Alternatively, for chemical stimulation, typically, an implantable drugpump transmits a pulse of medication through an infusion catheteraccording to the set of stimulation parameters and, in response to thepulse, infusion ports of the implanted infusion catheter deliver themedication to the specifically targeted nerve tissue in the spinal cordor particular identified peripheral nerve. The medication stimulates thespecifically targeted nerve tissue in the spinal cord or particularidentified peripheral nerve to mask or otherwise relieve pain in theaffected region of the body. The infusion ports typically must beprecisely positioned based on the location of the specifically targetednerve tissue in the spinal cord or particular peripheral nerve that isto be stimulated.

Of course, in many cases, chronic pain may be intractable other thanthrough highly invasive surgical procedures. For example, for chronicpain in the low back area associated with a herniated disc, a discectomyor other radical surgery may be required for adequate pain relief.However, such highly invasive surgical procedures involve a host ofundesirable consequences. These may include the significant cost of thesurgery itself, the risk of paralysis or death due to complicationsduring surgery, the trauma to the skin, muscles, nerves, and associatedanatomical structures and the resulting scarring, pain, and discomfortthat naturally results from the surgery, the significant rehabilitationtime and associated costs following the surgery, and other consequences.Perhaps worse, such highly invasive surgical procedures often do noteven completely suppress the chronic pain for which they were indicated.

SUMMARY OF THE INVENTION

Certain embodiments of the present invention may reduce or eliminatecertain problems and disadvantages associated with previous techniquesfor treating low back pain. Although treatment of low back pain isprimarily described, clinical results indicate that embodiments of thepresent invention may involve treatment of virtually any painful regionof the trunk or limbs.

According to one embodiment, a system for neurological stimulation ofperipheral nerve fibers to treat low back pain is provided. The systemincludes stimulation electrodes adapted to be implanted in tissueproximate a network of peripheral nerve fibers located in andinnervating a painful region of the low back area and to deliverelectrical stimulation pulses to the network of peripheral nerve fiberslocated in and innervating the painful region of the low back area. Thesystem also includes a stimulation source adapted for implantation intothe person's body and operable to generate electrical stimulation pulsesfor transmission to the electrodes for delivery to the network ofperipheral nerve fibers located in and innervating the painful region ofthe low back area to relieve pain in the painful region of the low backarea.

Particular embodiments of the present invention may provide one or moretechnical advantages. Certain embodiments may provide all, some, or noneof these advantages. Certain embodiments may provide one or more otheradvantages, one or more of which may be readily apparent to thoseskilled in the art from the figures, descriptions, and claims includedherein.

In certain embodiments, an implanted neurological stimulation system isused to electrically stimulate a network of peripheral nerve fiberslocated in and innervating the low back area to treat low back pain. Inparticular, electrodes are implanted inside a person's body in tissuesurrounding, overlying, or otherwise proximate the network of peripheralnerve fibers located in and innervating the painful region of the lowback area. For example, the electrodes may be located in the epidermis,the dermis, or the subcutaneous tissue surrounding, overlying, orotherwise proximate the network of peripheral nerve fibers located inand innervating the painful region of the low back area. The electrodesdeliver electrical stimulation pulses to the network of peripheral nervefibers located in and innervating the painful region of the low backarea, which may provide paresthesia or otherwise partially or completelysuppress the person's pain in the painful region of the low back area,which may in turn significantly increase the person's quality of life.For example, where a person suffers from chronic intractable pain due tosurgery, trauma, or other stress to the bones, musculature, nerves, orother anatomical structures in the low back area, the electrodes maydeliver electrical stimulation pulses to the network of peripheral nervefibers located in and innervating the painful region of the low backarea to relieve pain in the painful region of the low back area.

In contrast to prior techniques for treating low back pain requiringhighly invasive surgery, certain embodiments of the present inventionmay allow chronic intractable pain to be successfully treated withoutinvasive surgical procedures and their associated negative consequences,providing an important technical advantage. Furthermore, in contrast toprior techniques for treating pain in a particular region of the bodyrequiring the electrical stimulation lead to be implanted adjacent thespinal cord or a particular identified peripheral nerve such that theelectrodes are precisely located proximate specifically targeted nervetissue in the spinal cord or the particular identified peripheral nerve,certain embodiments of the present invention allow the lead to beimplanted in tissue surrounding, overlying, or otherwise proximate anetwork of peripheral nerve fibers located in and innervating thepainful region of the low back area without regard to the preciselocation of particular nerve tissue in the spinal cord or any particularidentified peripheral nerve. Among other benefits, for example, this maymake implanting the electrical stimulation lead and locating theelectrodes easier for the doctor and safer for the patient, providing animportant technical advantage.

In certain embodiments, a neurological stimulation system is used todeliver a medication or other chemical to the network of peripheralnerve fibers located in and innervating the painful region of the lowback area using an implanted infusion pump and catheter to chemicallystimulate the network of peripheral nerve fibers located in andinnervating the painful region of the low back area to relieve pain inthe low back area, in conjunction with or independent from anyelectrical stimulation of the network of peripheral nerve fibers locatedin and innervating the painful region of the low back area.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention andadvantages thereof, reference is now made to the following descriptiontaken in conjunction with the accompanying drawings, in which:

FIGS. 1A-1B illustrate example systems for neurological stimulation ofperipheral nerves to treat low back pain;

FIGS. 2A-2I illustrate example electrical stimulation leads that may beused to stimulate peripheral nerves to treat low back pain;

FIG. 3 illustrates example placement of the electrical stimulationsystem shown in FIGS. 1A-1B within a person's body;

FIG. 4 illustrates an example method for implanting the stimulationsystem of FIGS. 1A-1B into a person to stimulate peripheral nerves totreat low back pain;

FIGS. 5A-5E further illustrate an example method for implanting thestimulation system of FIGS. 1A-1B into a person to stimulate peripheralnerves to treat low back pain;

FIG. 6 illustrates an example stimulation set;

FIG. 7 illustrates a number of example stimulation programs, each ofwhich includes a number of stimulation sets; and

FIG. 8 illustrates example execution of a sequence of stimulation setswithin an example stimulation program.

DESCRIPTION OF EXAMPLE EMBODIMENTS

According to the present invention, a neurological stimulation system isused to stimulate peripheral nerves in a painful region of the low backarea to treat low back pain. Although treatment of low back pain isprimarily described, clinical results indicate that embodiments of thepresent invention may involve treatment of virtually any painful regionof the trunk or limbs.

In certain embodiments, an implanted neurological stimulation system isused to electrically stimulate a network of peripheral nerve fiberslocated in and innervating the low back area to treat low back pain. Inparticular, electrodes are implanted inside a person's body in tissuesurrounding, overlying, or otherwise proximate the network of peripheralnerve fibers located in and innervating the painful region of the lowback area. For example, the electrodes may be located in the epidermis,the dermis, or the subcutaneous tissue surrounding, overlying, orotherwise proximate the network of peripheral nerve fibers located inand innervating the painful region of the low back area. The electrodesdeliver electrical stimulation pulses to the network of peripheral nervefibers located in and innervating the painful region of the low backarea, which may provide paresthesia or otherwise partially or completelysuppress the person's pain in the painful region of the low back area,which may in turn significantly increase the person's quality of life.For example, where a person suffers from chronic intractable pain due tosurgery, trauma, or other stress to the bones, musculature, nerves, orother anatomical structures in the low back area, the electrodes maydeliver electrical stimulation pulses to the network of peripheral nervefibers located in and innervating the painful region of the low backarea to relieve pain in the painful region of the low back area.

In contrast to prior techniques for treating low back pain requiringhighly invasive surgery, certain embodiments of the present inventionmay allow chronic intractable pain to be successfully treated withoutinvasive surgical procedures and their associated negative consequences,providing an important technical advantage. Furthermore, in contrast toprior techniques for treating pain in a particular region of the bodyrequiring the electrical stimulation lead to be implanted adjacent thespinal cord or a particular identified peripheral nerve such that theelectrodes are precisely located proximate specifically targeted nervetissue in the spinal cord or the particular identified peripheral nerve,certain embodiments of the present invention allow the lead to beimplanted in tissue surrounding, overlying, or otherwise proximate anetwork of peripheral nerve fibers located in and innervating thepainful region of the low back area without regard to the preciselocation of particular nerve tissue in the spinal cord or any particularidentified peripheral nerve. Among other benefits, for example, this maymake implanting the electrical stimulation lead and locating theelectrodes easier for the doctor and safer for the patient, providing animportant technical advantage.

In certain embodiments, a neurological stimulation system is used todeliver a medication or other chemical to the network of peripheralnerve fibers located in and innervating the painful region of the lowback area using an implanted infusion pump and catheter to chemicallystimulate the network of peripheral nerve fibers located in andinnervating the painful region of the low back area to relieve pain inthe low back area, in conjunction with or independent from anyelectrical stimulation of the network of peripheral nerve fibers locatedin and innervating the painful region of the low back area.

FIGS. 1A-1B illustrate example systems 10 for neurological stimulationof peripheral nerves to treat low back pain. Stimulation system 10generates and applies a stimulus to a network of peripheral nerve fiberslocated in and innervating a painful region of the low back area torelieve pain in the painful region of the low back area. In generalterms, stimulation system 10 includes an implantable electricalstimulation source 12 and one or more implantable electrical stimulationleads 14 for applying electrical stimulation pulses to the network ofperipheral nerve fibers located in and innervating the painful region ofthe low back area. In operation, both of these primary components areimplanted in the person's body, as discussed below with reference toFIGS. 3, 4, and 5A-5E. In certain embodiments, stimulation source 12 iscoupled directly to a connecting portion 16 of electrical stimulationlead 14. In certain other embodiments, stimulation source 12 is notcoupled directly to stimulation lead 14 and stimulation source 12instead communicates with stimulation lead 14 via a wireless link. Incertain other embodiments, stimulation source 12 and electrodes 18 arecontained in an “all-in-one” microstimulator or other unit, such as aBion® microstimulator manufactured by Advanced Bionics Corporation. Inany case, stimulation source 12 controls the electrical stimulationpulses transmitted to electrodes 18 (which may be located on astimulating portion 20 of an electrical stimulation lead 14), implantedproximate the network of peripheral nerve fibers, according toappropriate stimulation parameters (e.g., duration, amplitude orintensity, frequency, etc.). A doctor, the patient, or another user ofstimulation source 12 may directly or indirectly input or modifystimulation parameters to specify or modify the nature of the electricalstimulation provided.

In one embodiment, as shown in FIG. 1A, stimulation source 12 includesan implantable pulse generator (IPG). An example IPG may be onemanufactured by Advanced Neuromodulation Systems, Inc., such as theGenesis® System, part numbers 3604, 3608, 3609, and 3644. In anotherembodiment, as shown in FIG. 1B, stimulation source 12 includes animplantable wireless receiver. An example wireless receiver may be onemanufactured by Advanced Neuromodulation Systems, Inc., such as theRenew® System, part numbers 3408 and 3416. The wireless receiver iscapable of receiving wireless signals from a wireless transmitter 22located external to the person's body. The wireless signals arerepresented in FIG. 1B by wireless link symbol 24. A doctor, thepatient, or another user of stimulation source 12 may use a controller26 located external to the person's body to provide control signals foroperation of stimulation source 12. Controller 26 provides the controlsignals to wireless transmitter 22, wireless transmitter 22 transmitsthe control signals and power to the wireless receiver of stimulationsource 12, and stimulation source 12 uses the control signals to varyone or more stimulation parameters of the electrical stimulation pulsestransmitted through electrical stimulation lead 14 to the stimulationsite. An example wireless transmitter 122 may be one manufactured byAdvanced Neuromodulation Systems, Inc., such as the Renew® System, partnumbers 3508 and 3516.

As discussed above, instead or in addition to providing electricalstimulation, a neurological stimulation system may include animplantable infusion pump (not shown) and an implantable infusioncatheter (not shown) with one or more infusion ports for the delivery ofa medication or other suitable chemical to the network of peripheralnerve fibers located in and innervating the painful region of the lowback area. In certain embodiments, appropriate infusion pumps 12 a mayinclude those illustrated and described in U.S. Pat. Nos. 4,772,263 and6,666,845, which are hereby incorporated by reference herein as if fullyillustrated and described herein. Where appropriate, an electricalstimulation lead 14 may be formed with a hollow inner channel and one ormore infusion ports, and may be adapted for coupling to an infusionpump, thereby serving as a combined electrical stimulation lead andinfusion catheter.

FIGS. 2A-2I illustrate example electrical stimulation leads 14 that maybe used to stimulate peripheral nerves to treat low back pain. Asdescribed above, each of the one or more leads 14 that may beincorporated in stimulation system 10 includes electrodes 18 adapted tobe positioned in tissue surrounding, overlying, or otherwise proximatethe network of peripheral nerve fibers located in and innervating thepainful region of the low back area and used to deliver electricalstimulation pulses to the network of peripheral nerve fibers located inand innervating the painful region of the low back area in response toreceiving the electrical stimulation pulses from stimulation source 12.A percutaneous lead 14, such as example leads 14 a-d, includes one ormore circumferential electrodes 18 spaced apart from one another alongthe length of lead 14. Circumferential electrodes 18 emit electricalstimulation energy generally radially in all directions. A laminotomy orpaddle style lead 14, such as example leads 14 e-i, includes one or moredirectional electrodes 18 spaced apart from one another along onesurface of lead 14. Directional electrodes 18 emit electricalstimulation energy in a direction generally perpendicular to the surfaceof lead 14 on which they are located, which may be desirable fordirecting the electrical stimulation in a particular direction to bettertarget particular tissue. Although various types of leads 14 are shownas examples, the present invention contemplates stimulation system 10including any suitable type of lead 14 in any suitable number. Inaddition, leads 14 may be used singly or in combination. For example,unilateral stimulation of the low back may be accomplished using asingle lead 14 implanted in one side of the low back, while bilateralstimulation of the low back may be accomplished using two leads 14implanted in opposite sides of the low back.

FIG. 3 illustrates example placement of the electrical stimulationsystem 10 shown in FIGS. 1A-1B within a person's body 30. Electricalstimulation lead 14 is implanted in or under the person's skin (i.e., inthe epidermis, dermis, or subcutaneous tissue) surrounding, overlying,or otherwise proximate the network of peripheral nerve fibers located inand innervating the painful region of the low back area. In certainembodiments, electrical stimulation lead 14 is positioned such that oneor more electrodes 18 are located superior to fascia overlying thenetwork of peripheral nerve fibers located in and innervating thepainful region of the low back area. Stimulation source 12 is implantedwithin a subcutaneous pocket within the person's torso (such as in ornear the chest or buttocks), and connecting portion 16 is tunneled, atleast in part, subcutaneously to connect stimulation source 12 with theelectrical stimulation lead 14. However, stimulation source 12 may belocated at any suitable location within the person's body according toparticular needs. In certain embodiments, an implantable infusioncatheter (not shown) and infusion pump (not shown) may be implanted inlocations and in a manner analogous to implantation of electricalstimulation lead 14 and stimulation source 12. For example, similar toplacement of electrodes 18 of an electrical stimulation lead 14,infusion ports of the infusion catheter may be located proximate thenetwork of peripheral nerve fibers located in and innervating thepainful region of the low back area.

FIG. 4 illustrates an example method for determining the location forelectrical stimulation lead 14 and implanting the stimulation system 10of FIGS. 1A-1B into a person for stimulating peripheral nerves to treatlow back pain. At step 50, as further illustrated in FIG. 5A, a painfulregion 100 of the low back area is determined in consultation with thepatient and marked or otherwise indicated on the person's body. As oneexample, the patient, the doctor, or another clinical professional mayuse a pen or other marker to mark painful region 100 of the low backarea directly on the person's skin. As one other example, the doctor oranother clinical professional may use a light fixture with an adjustableaperture to further illuminate painful region 100 of the low back area.In a particular embodiment, for optimal pain relief, electricalstimulation lead 14 is implanted in tissue surrounding, overlying, orotherwise proximate the network of peripheral nerve fibers located inand innervating a sub-region of the low back area, within region 100,that the patient identifies as being particularly sensitive to pain(i.e. having the greatest hyperalgesia). Thus, at step 52, as furtherillustrated in FIG. 5B, a sub-region 102 of the low back area that isparticularly sensitive to pain is determined and sub-region 102 of thelow back area is marked or otherwise indicated on the person's body. Forexample, the patient, the doctor, or another clinical professional maymark or otherwise indicate sub-region 102 in the same manner as region100. Identifying sub-region 102 may include identifying an approximateepicenter of the pain within region 100. Pre-operatively, while thepatient is positioned on the operating room table, the patient shouldpreferably be asked to confirm the identification of sub-region 102(including any identified epicenter), since the painful region or thespatial relationship between the marked skin and the painful region maymove as a result of changes in position. Although example region 100 andsub-region are illustrated, the present invention contemplates anysuitable regions 100 and sub-regions 102 according to particularcircumstances. Preferably, the implant site of stimulation source 12 andthe paths of the one or more electrical stimulation leads 14 are plannedbefore implantation occurs. Consideration should preferably be made foravoiding the painful region to be treated or other regions ofsensitivity.

At steps 54-58, electrical stimulation lead 14 is implanted in tissuesurrounding, overlying, or otherwise proximate the network of peripheralnerve fibers located in and innervating painful region 100 of the lowback area, preferably the network of peripheral nerve fibers located inand innervating sub-region 102 of the low back area. For example,electrical stimulation lead 14 may be implanted in the epidermis, thedermis, or the subcutaneous tissue proximate the network of peripheralnerve fibers located in and innervating sub-region 102 of the low backarea. In a particular embodiment, electrical stimulation lead 14 isimplanted approximately one centimeter deep, in a tissue plane lyingbetween the dermal and subdermal layers. In general, the closerelectrodes 18 are to the surface of the skin, the less likely thestimulation will cause contractions of the underlying muscles. Thus,implantation of electrical stimulation lead 14 more superficially to thesubdermal layer (i.e., in the epidermis or dermis) may be desirable inother embodiments if unwanted stimulation of muscle nerve fibers is aconcern. Preferably, electrical stimulation lead 14 will traverse region100 such that the stimulation pulse electric field spans and provideseffective stimulation over at least 90% of region 100 and 100% ofsub-region 102. In a particular embodiment, an electrical stimulationlead 14 having four electrodes 18 may effectively span an areaapproximately the size of a tennis ball. If region 100 is too large forthe effective span of electrodes 18, then optimal pain relief may not berealized. Preferably, electrical stimulation lead 14 should be placedsuch that it traverses the longest axis of region 100 and through theapproximate center of sub-region 102 (including over any identifiedepicenter). Alternatively, if the patient is experiencing allodynia overregion 100, then region 100 may need to be bracketed with two or moreelectrical stimulation leads 14 placed about the perimeter of region100. Electrical stimulation lead 14 may be implanted percutaneously(either directly or through a suitable introducer where appropriate),surgically, or in any other manner.

For example, at step 54 as further illustrated in FIG. 5C, a needle 104may be inserted into sub-region 102 of the low back area such that tip106 of needle 104 is located in the epidermis, the dermis, or thesubcutaneous tissue (collectively, tissue 110) proximate the network ofperipheral nerve fibers 112 located in and innervating sub-region 102.In the particular embodiment in which electrical stimulation lead 14 isimplanted approximately one centimeter deep, in a tissue plain lyingbetween the dermal and subdermal layers, needle 104 may visibly “tent”the skin as it is being advanced to the targeted implant site. In thisparticular embodiment, needle 104 should preferably advance with minimalresistance. If the resistance against needle 104 is too great, it mayindicate that needle 104 is not in the proper tissue plane (i.e., is inthe epidermal or dermal layer) or that the patient's epidermal or dermallayer is abnormally thick. Further, if needle 104 is in the epidermal ordermal layer, the skin may actually dimple at the needle insertion pointand along the path to the targeted implant site. As discussed above,implantation of electrical stimulation lead 14 in the epidermal ordermal layer may be desirable in other particular embodiments whereunwanted stimulation of muscle nerve fibers is a concern.

Continuing the example, at step 56 as further illustrated in FIG. 5D,electrical stimulation lead 14 may be inserted through needle 104 intosub-region 102 of the low back area such that electrodes 18 of lead 14are located superior to fascia 108 or otherwise in tissue 110 proximatethe network of peripheral nerve fibers 112 located in and innervatingsub-region 102.

Continuing the example, at step 58 as further illustrated in FIG. 5E,needle 104 may then be removed leaving electrical stimulation lead 14 inposition with electrodes 18 located superior to fascia 108 or otherwisein tissue 110 proximate the network of peripheral nerve fibers 112located in and innervating sub-region 102.

As an alternative example, after needle 104 is inserted at step 54, aguide wire (not shown) may be inserted through needle 104 into position,needle 104 may be removed, an introducer (not shown) may be advancedalong the guide wire into position, electrical stimulation lead 14 maybe inserted through the introducer into position, and the introducer maythen be removed leaving lead 14 in position with electrodes 18 againlocated superior to fascia 108 or otherwise in tissue 110 proximate thenetwork of peripheral nerve fibers 112 located in and innervatingsub-region 102.

Preferably, electrical stimulation lead 14 should be anchored using asuitable anchoring technique. Anchoring electrical stimulation lead 14for peripheral nerve stimulation may be a challenge due to the slightdifferences between the anatomies of patients, in particular the tissueplanes in which electrical stimulation lead 14 is to be implanted. Incontrast, anchoring an electrical stimulation lead 14 used for spinalcord stimulation as it exits the epidural space may be morestraightforward. In a particular embodiment, two anchors are utilized toanchor electrical stimulation lead 14—a “butterfly” anchor such as onemanufactured by Advanced Neuromodulation Systems, Inc., part number64-1105, and a “long” anchor such as one manufactured by AdvancedNeuromodulation Systems, Inc., part number 64-1106. After lead placementis finalized, a small incision is made at the point where needle 104exits the skin and dissection is performed down to the fascial plane.The wings or tabs of the butterfly anchor are cut off and the butterflyanchor is placed on the lead body and sutured to the dermal or subdermaltissue layer superficially and perpendicular to the surface of the skin.The long anchor is then threaded onto electrical stimulation lead 14.Electrical stimulation lead 14 is looped around to the fascial surfacewith the long anchor positioned flat against the fascial plane and thensutured to the fascia. Once the anchors have been secured, preferablyafter complete implantation of electrical stimulation lead 14 andstimulation source 12, the anchoring pocket can be closed. Although aparticular anchoring technique is described in detail, other embodimentsmay involve other suitable anchoring techniques according to particularneeds.

At step 60, stimulation source 12 is activated, which generates andsends electrical stimulation pulses for delivery via electrodes 18 tothe network of peripheral nerve fibers 112 located in and innervatingsub-region 102 of the low back area. A doctor, the patient, or anotheruser of stimulation source 12 may directly or indirectly input or modifyone or more stimulation parameters to specify or modify the nature ofthe stimulation provided. At step 62, the person indicates whether thelow back pain is partially or completely suppressed by electricalstimulation system 10. In certain embodiments, the patient may or maynot experience paresthesia. For example, the electrical stimulationmight not stimulate the network of peripheral nerve fibers 112 locatedin and innervating sub-region 102 of the low back area to an extentnecessary to cause paresthesia or might not stimulate nerve fibers thatwould need to be stimulated to cause paresthesia. If the low back painis not adequately suppressed, electrical stimulation lead 14 may bemoved incrementally at step 64 until the person indicates that the lowback pain is adequately suppressed. Once electrical stimulation lead 14has been properly positioned such that the low back pain is adequatelysuppressed, stimulation source 12 is implanted at step 66. Stimulationsource 12 may be implanted before, after, or even without such a trialstimulation period, according to particular needs. In certainembodiments, trial peripheral nerve stimulation can be performed over alonger period of time, up to thirty days for example, than trial spinalcord stimulation due to a reduced risk of complications. For example, ina particular embodiment in which electrical stimulation lead 14 isimplanted in a tissue plain lying between the dermal and subdermallayers, subsequent sequela such as infections are rare and, when theyoccur, can be easily managed. A longer trial stimulation period may givethe patient a longer opportunity to become accustomed to the stimulationsensation, a longer period in which to initiate repositioning of thelead if necessary, and a longer opportunity to try different stimulationprograms to optimize the pain relief. Of course, if after an extendedtrial stimulation period the patient continues to describe thestimulation sensation as uncomfortable or bothersome, then the trialshould be considered unsuccessful and another course of therapyconsidered.

The implant site is typically a subcutaneous pocket formed to receiveand house stimulation source 12. The implant site is usually positioneda distance away from the insertion site, such as in the chest, buttocks,or another suitable location. However, a suitably small stimulationsource 12 may be used to allow stimulation source 12 to be implanted ator very near the stimulation site. Connecting portion 16 of electricalstimulation lead 14 extends from the lead insertion site to the implantsite at which stimulation source 12 is implanted. Where appropriate, anextension may be used to connect electrical stimulation lead 14 tostimulation source 12. A doctor, the patient, or another user ofstimulation source 12 may thereafter directly or indirectly input ormodify one or more stimulation parameters to specify the nature of thestimulation provided.

In certain embodiments, an implantable infusion catheter (not shown) andinfusion pump (not shown) may be implanted in locations and in a manneranalogous to implantation of electrical stimulation lead 14 andstimulation source 12. For example, similar to placement of electrodes18 of an electrical stimulation lead 14, one or more infusion ports ofthe infusion catheter may be located superior to fascia 108 or otherwisein tissue 110 proximate the network of peripheral nerve fibers 112located in and innervating sub-region 102 of the low back area. Whereappropriate, an electrical stimulation lead 14 may be formed with ahollow inner channel and one or more infusion ports, and may be adaptedfor coupling to an infusion pump, thereby serving as a combinedelectrical stimulation lead and infusion catheter.

Although example steps are illustrated and described, the presentinvention contemplates two or more steps taking place substantiallysimultaneously or in a different order. In addition, the presentinvention contemplates using methods with additional steps, fewer steps,or different steps, so long as the steps remain appropriate forimplanting an example stimulation system 10 into a person for electricalstimulation to treat low back pain.

FIG. 6 illustrates an example stimulation set 150. One or morestimulation sets 150 may be provided, each stimulation set 150specifying a number of stimulation parameters for stimulation set 150.For example, as described more fully below with reference to FIGS. 7-8,multiple stimulation sets 150 may be executed in an appropriate sequenceaccording to a pre-programmed or randomized stimulation program.Stimulation parameters for a stimulation set 150 may include anamplitude or intensity, a frequency, phase information, and a pulsewidth for each of a series of stimulation pulses that electrodes 18 areto deliver to the network of peripheral nerve fibers located in andinnervating the painful region of the low back area during a timeinterval during which stimulation set 150 is executed, along with apolarity 152 for each electrode 18 in each stimulation pulse. Ingeneral, electric fields are generated between adjacent electrodes 18having different polarities 152 to deliver electrical stimulation pulsesto the network of peripheral nerve fibers located in and innervating thepainful region of the low back area. Stimulation parameters may alsoinclude a pulse shape, for example, biphasic cathode first, biphasicanode first, or any other suitable pulse shape.

The polarity for an electrode 18 at a time 154 beginning a correspondingstimulation pulse or sub-interval within a stimulation pulse may be apositive polarity 152 such that current flows out of the electrode 18into the tissue (from which the current will return through one or moreother electrodes 18), a negative polarity 152 such that current flowsinto the electrode 18 from the tissue (into which the current wasdelivered from one or more other electrodes 18), or a zero (i.e., “highimpedance) polarity such that the electrode 18 is essentially “turnedoff” and zero or substantially zero current flows out of or into theelectrode 18. Thus, the polarity 152 of an electrode determines whethercurrent will flow through the electrode 18 and in which direction. Incertain embodiments, the polarity 152 of an electrode 18 may be definedin terms of voltage, in which case the polarity 152 may be relativelypositive polarity 152, a relatively negative polarity 152, or anintermediate polarity 152 between the relatively positive polarity 152and relatively negative polarity 152. For example, the relativelypositive polarity 152 may involve a positive voltage, the relativelynegative polarity 152 may involve a negative voltage, and the relativelyintermediate polarity 152 may involve a zero voltage. As anotherexample, the relatively positive polarity 152 may involve a firstnegative voltage, the relatively negative polarity 152 may involve asecond negative voltage more negative than the first negative voltage,and the relatively intermediate polarity 152 may involve a negativevoltage between the first and second negative voltages. The availabilityof three distinct polarities 152 for an electrode 18 may be referred toas “tri-state” electrode operation. The polarity 152 for each electrode18 may change for each of the sequence of times 154 corresponding tostimulation pulses or to sub-intervals within a stimulation pulseaccording to the stimulation parameters specified for the stimulationset 150. For example, as is illustrated in FIG. 7 for an examplestimulation set 150 for a stimulation lead 14 with sixteen electrodes18, the polarities 152 of the sixteen electrodes 18 may change for eachof the sequence of times 154. In the example of FIG. 7, a positive orrelatively positive polarity 152 is represented using a “1,” a negativeor relatively negative polarity 152 is represented using a “−1,” and azero or relatively intermediate polarity 152 is represented using a “0,”although any suitable values or other representations may be used.

FIG. 7 illustrates a number of example stimulation programs 156, eachincluding a number of stimulation sets 150. As described above, eachstimulation set 150 specifies a number of stimulation parameters forstimulation set 150. In one embodiment, in each stimulation program 156,stimulation system 10 consecutively executes the sequence of one or morestimulation sets 150 associated with stimulation program 156. Thesequence may be executed only once, repeated a specified number oftimes, or repeated an unspecified number of times within a specifiedtime period. For example, as is illustrated in FIG. 8 for the thirdexample stimulation program 156 c including eight stimulation sets 150,each of the eight stimulation sets 150 is consecutively executed insequence. Although the time intervals 158 (t₁-t₀, t₂-t₁, etc.) duringwhich the stimulation sets 150 are executed are shown as being equal,the present invention contemplates a particular stimulation set 150being executed over a different time interval 158 than one or more otherstimulation sets 150 according to particular needs.

Although stimulation system 10 is illustrated by way of example asaccommodating up to twenty-four stimulation programs 156 each includingup to eight stimulation sets 150, the present invention contemplates anyappropriate number of stimulation programs 156 each including anyappropriate number of stimulation sets 150. For example, in a verysimple case, a single stimulation program 156 may include a singlestimulation set 150, whereas in a very complex case more thantwenty-four stimulation programs 156 may each include more than eightstimulation sets 150.

In one embodiment, stimulation system 10 executes only a singlestimulation program 156 in response to user selection of thatstimulation program for execution. In another embodiment, during astimulation period, stimulation system 10 executes a sequence ofpre-programmed stimulation programs 156 for each lead 14 until thestimulation period ends. Depending on the length of the stimulationperiod and the time required to execute a sequence of stimulationprograms 156, the sequence may be executed one or more times. Forexample, the stimulation period may be defined in terms of apredetermined number of cycles each involving a single execution of thesequence of stimulation programs 156, the sequence of stimulationprograms 156 being executed until the predetermined number of cycles hasbeen completed. As another example, the stimulation period may bedefined in terms of time, the sequence of stimulation programs 156 beingexecuted until a predetermined time interval has elapsed or the patientor another user manually ends the stimulation period. Although asequence of stimulation programs 156 is described, the present inventioncontemplates a single stimulation program being executed one or moretimes during a stimulation period according to particular needs.Furthermore, the present invention contemplates each stimulation program156 being executed substantially immediately after execution of aprevious stimulation program 156 or being executed after a suitable timeinterval has elapsed since completion of the previous stimulationprogram 156. Where stimulation system 10 includes multiple leads 14,stimulation programs 156 for a particular lead 14 may be executedsubstantially simultaneously as stimulation programs 156 for one or moreother leads 14, may be alternated with stimulation programs 156 for oneor more other leads 14, or may be arranged in any other suitable mannerwith respect to stimulation programs 156 for one or more other leads 14.

In general, each stimulation program 156 may, but need not necessarily,be set up for electrical stimulation of a different network ofperipheral nerve fibers located in and innervating the painful region ofthe low back area. For example, one or more stimulation programs 156 maybe set up for therapeutic electrical stimulation of one network ofperipheral nerve fibers located in and innervating the painful region ofthe low back area and one or more other stimulation programs 156 may beset up for electrical stimulation of another network of peripheral nervefibers located in and innervating the painful region of the low backarea to improve the overall pain relief provided.

The present invention contemplates any suitable circuitry withinstimulation source 12 for generating and transmitting signals forelectrical stimulation of peripheral nerves to treat low back pain.Example circuitry which may be used is illustrated and described in U.S.Pat. No. 6,609,031 B1, which is hereby incorporated by reference hereinas if fully illustrated and described herein.

Although the present invention has been described above in connectionwith several embodiments, a plethora of changes, substitutions,variations, alterations, transformations, and modifications may besuggested to one skilled in the art, and it is intended that the presentinvention encompass such changes, substitutions, variations,alterations, transformations, and modifications as fall within thespirit and scope of the appended claims.

1. A method for treating pain, comprising: positioning one or morestimulation leads with a plurality of electrodes being disposed in apainful region in a patient's body having an approximate epicenter ofpain, wherein positioning comprises positioning the plurality ofelectrodes in the epidermis, dermis, or subcutaneous tissue superior tofascia containing a network of localized peripheral nerve fibers locatedin and influencing the painful region without regard to a specific oridentifiable nerve or nerve branch; using an electrical stimulationsource implanted in a person's body, generating electrical pulses fortransmission to the plurality of electrodes; and in response to theelectrical stimulation pulses transmitted from the stimulation sourceimplanted in the person's body, treating the patient's pain by using theplurality of electrodes to stimulate the network of localized sensorynerve fibers located in and influencing the painful region of thepatient's body.
 2. The method of claim 1 wherein the painful regioncomprises a region of the trunk.
 3. The method of claim 1 wherein thepainful region comprises a region of the limbs.
 4. The method of claim 1wherein the painful region comprises a region of the back.
 5. The methodof claim 1 wherein the plurality of electrodes are positionedimmediately proximate to an epicenter of pain.
 6. The method of claim 1,wherein the stimulation source generates the stimulation pulsesaccording to one or more stimulation sets each specifying a plurality ofstimulation parameters to relieve pain in the painful region.
 7. Themethod of claim 6, wherein the stimulation parameters for a stimulationset comprising a polarity for each electrode at each of one or moretimes within a stimulation pulse for the stimulation set.
 8. The methodof claim 1, wherein the stimulation source generates the stimulationpulses according to a plurality of stimulation programs each comprisingone or more stimulation sets, each stimulation set specifying aplurality of stimulation parameters to relieve pain in the painfulregion.
 9. The method of claim 1, wherein the electrical stimulationpulses of the network of localized peripheral nerve fibers providesparesthesia with respect to the painful region.
 10. The method of claim1 further comprising identifying a sub-region having an approximateepicenter of pain within a region of pain and positioning the one ormore stimulation leads such that the plurality of electrodes aredisposed in the sub-region and substantially aligned along a greatestaxis of the region of pain.
 12. The method of claim 1 further comprisingat least one or more of the stimulation leads being adapted to comprisea plurality of infusion ports and capable of coupling to an infusionpump.
 13. The method of claim 12 further comprising using an implantableinfusion pump to deliver a medication or chemical to the network oflocalized sensory nerve fibers located in and influencing the painfulregion of the patient's body.
 14. A method for treating back pain,comprising: positioning one or more stimulation leads with a pluralityof electrodes being disposed in a sub-region having an approximateepicenter of pain of back pain, wherein positioning comprisespositioning the plurality of electrodes in the epidermis, dermis, orsubcutaneous tissue superior to fascia containing a network of localizedperipheral nerve fibers located in and influencing the painful regionwithout regard to a specific or identifiable nerve or nerve branch;using an electrical stimulation source implanted in a person's body,generating electrical pulses for transmission to the plurality ofelectrodes; and in response to the electrical stimulation pulsestransmitted from the stimulation source implanted in the person's body,treating the patient's back pain by using the plurality of electrodes tostimulate the network of localized sensory nerve fibers located in andinfluencing the painful region.
 15. A method for treating pain,comprising: positioning one or more infusion catheters with a pluralityof infusion ports being disposed in a painful region in a patient's bodyhaving an approximate epicenter of pain, wherein positioning comprisespositioning the plurality of infusion ports in the epidermis, dermis, orsubcutaneous tissue superior to fascia containing a network of localizedperipheral nerve fibers located in and influencing the painful regionwithout regard to a specific or identifiable nerve or nerve branch;using an implantable infusion pump to deliver a medication or chemicalto the plurality of infusion ports; and in response to the medication orchemical, treating the patient's pain by using the plurality of infusionports to deliver medication or chemical to stimulate the network oflocalized sensory nerve fibers located in and influencing the painfulregion of the patient's body.